As unlicensed use for a TV frequency band which is not used and is empty, which is called a TV white space (TVWS) is permitted by the Federal Communication Commission (FCC), a research into spectrum sharing technology in a corresponding frequency band is in progress worldwide.
In order to use a TV band device (TVBD) which is a TV band wireless device in a channel which is the same as or adjacent to a channel used by a DTV which is a primary user in the TV band, the TVBD needs to be operated with a predetermined protection spacing distance from a DTV service boundary point. As described above, the number of available channels which are usable in a frequency sharing band by the TVBD which is a secondary user is determined according to the number of channels presently used by the DTV which is the primary user, the protection spacing distance, and the like.
In the case of a broadcasting service which is the primary user, a case where the channel needs to be reassigned for an efficient operation of a system and frequency rearrangement occurs. In this case, since the number of available channels which are usable by the TVBD which is the secondary user is not considered, inefficiency upon channel reassignment is increased.